In one class of high pressure liquid pumps, output from the pump is controlled by throttling the inlet with an electronically controlled metering valve. As a consequence, cavitation bubbles are generated when the output of the pump is controlled to be less than the volume displaced with each reciprocation of the pump plunger. One application for such a pump is in a fuel system that utilizes a common rail and a high-pressure fuel pump to pressurize the rail. In this specific example, the pump is driven directly by the engine, and the output from the pump is controlled by changing the inlet flow area via the inlet throttle valve.
When the inlet throttle valve reduces the flow area to the plunger cavity, cavitation bubbles can be generated in the vicinity of the throttle valve, or potentially elsewhere, and travel to the plunger cavity to occupy part of the volume created by the retracting plunger of the pump. When the cavitation bubbles collapse adjacent a surface, cavitation erosion can occur. In some instances, cavitation erosion can occur at undesirable locations, such as the inlet port passage or in the vicinity of valve seats. Depending upon where the cavitation damage occurs, and the extent of that damage, the pump performance can be undermined, and maybe more importantly, the eroded particles can find their way into fuel injectors possibly causing even more serious problems.
U.S. Pat. No. 8,202,064 B2 to Tian et al. is directed to an inlet throttle controlled liquid pump with cavitation damage avoidance feature. Tian et al. propose a specially shaped and sized cavitation flow adjuster extending from a valve member in a passive inlet check valve. A flow pattern is apparently formed by the valve in a way that encourages cavitation bubble collapse away from surfaces that could result in unacceptable cavitation damage to the pump. While Tian et al. appear to have provided advancements over the state of the art, additional developments relating to cavitation mitigation would be welcomed in the industry.